Etymology From Middle English probable, from Old French probable, from Latin probābilis (“that may be proved, credible”), from probāre (“to test, examine”); see probe, probity, prove. Compare recent doublet provable.
1
Likely or most likely to be true.
It's probable that it will rain tomorrow.
The probable source of the failure was the mass of feathers in the intake manifold.
1 more example
A major accident and embezzlement of its funds seem to have been the only disasters it escaped; and as to the latter, the most probable reason is that it never had any quantity of funds worth embezzling.1959 October 23, Michael Robbins, “The Isle of Wight (Newport Junction) Railway”, in Railway Magazine, page 721:
2
Likely to happen.
With all the support we have, success is looking probable.
3
Supporting, or giving ground for, belief, but not demonstrating.
probable evidence1765–1769, William Blackstone, Commentaries on the Laws of England, (please specify |book=I to IV), Oxford, Oxfordshire: […] Clarendon Press, →OCLC:
From an examination of the Teutonic words for "temple" Grimm has made it probable that amongst the Germans the oldest sanctuaries were natural woods.1890, James George Frazer, The Golden Bough, volume 2, page 8:
Etymology From Middle English probable, from Old French probable, from Latin probābilis (“that may be proved, credible”), from probāre (“to test, examine”); see probe, probity, prove. Compare recent doublet provable.
1
Something that is likely.
Four of the 32 251 Ku aircraft turned back, but the other 28 fought for 20 minutes against a reported 100 enemy aircraft, claiming 18 destroyed and five probables.2013, Ikuhiko Hata, Yasuho Izawa, Christopher Shores, Japanese Naval Fighter Aces 1932-45, page 57:
2
A person who is likely to appear or do a certain thing.